Platelets or thrombocytes are a component of blood whose function is to react to bleeding from blood vessel injury by clumping, thereby initiating a blood clot. Platelets have no cell nucleus; they are fragments of cytoplasm derived from the megakaryocytes of the bone marrow or lung, which then enter the circulation. Platelets are found only in mammals, whereas in other vertebrates, thrombocytes circulate as intact mononuclear cells.
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin.
Habu (波布) is a Ryukyuan name referring to certain venomous snakes:
Disintegrins are a family of small proteins from viper venoms that function as potent inhibitors of both platelet aggregation and integrin-dependent cell adhesion.
Protobothrops mucrosquamatus is a venomous pit viper species endemic to Asia. Common names include: brown-spotted pit viper, Taiwanese habu and pointed-scaled pit viper. No subspecies are currently recognized. The species was first described by Theodore Cantor in 1839.
Ristocetin is a glycopeptide antibiotic, obtained from Amycolatopsis lurida, previously used to treat staphylococcal infections. It is no longer used clinically because it caused thrombocytopenia and platelet agglutination. It is now used solely to assay those functions in vitro in the diagnosis of conditions such as von Willebrand disease (vWD) and Bernard–Soulier syndrome. Platelet agglutination caused by ristocetin can occur only in the presence of von Willebrand factor multimers, so if ristocetin is added to blood lacking the factor, the platelets will not clump.
Ancrod is a defibrinogenating agent derived from the venom of the Malayan pit viper. Defibrinogenating blood produces an anticoagulant effect. Ancrod is not approved or marketed in any country. It is a thrombin-like serine protease.
β2-glycoprotein 1, also known as beta-2 glycoprotein 1 and Apolipoprotein H (Apo-H), is a 38 kDa multifunctional plasma protein that in humans is encoded by the APOH gene. One of its functions is to bind cardiolipin. When bound, the structure of cardiolipin and β2-GP1 both undergo large changes in structure. Within the structure of Apo-H is a stretch of positively charged amino acids, Lys-Asn-Lys-Glu-Lys-Lys, are involved in phospholipid binding.
In enzymology, an L-amino acid oxidase (LAAO) (EC 1.4.3.2) is an enzyme that catalyzes the chemical reaction.
Platelet glycoprotein Ib alpha chain also known as glycoprotein Ib (platelet), alpha polypeptide or CD42b, is a protein that in humans is encoded by the GP1BA gene.
Glycoprotein IX (platelet) (GP9) also known as CD42a (Cluster of Differentiation 42a), is a human gene.
Cerastocytin is a thrombin-like serine protease in snake venom.
Ovophis okinavensis, commonly known as the hime habu (ヒメハブ), Ryukyu Island pit viper, and the Okinawan pitviper, is a venomous pitviper species found in the Ryukyu Islands of Japan. No subspecies are currently recognized.
Latisemin is a cysteine-rich secretory protein that can be isolated from the venom of the Black-banded sea krait, a sea snake indigenous to the warmer waters of the western Pacific Ocean. It is a toxin that inhibits cyclic nucleotide-gated ion channels and blocks L-type calcium channels, thereby reducing smooth muscle contraction.
The ristocetin-induced platelet aggregation (RIPA) is an ex vivo assay for live platelet function. It measures platelet aggregation with the help of von Willebrand factor (vWF) and exogenous antibiotic ristocetin added in a graded fashion. It is similar to the ristocetin cofactor assay but has the added benefit in that it helps in the diagnosis of type 2B/pseudo von Willebrand disease (vWD) and Bernard–Soulier syndrome because it uses patient's live endogenous platelets, whereas ristocetin cofactor assay tests the function of only the vWF and not the platelets. Ristocetin cofactor assay uses the patient's platelet poor plasma and adds ristocetin and exogenous formalin-fixed platelets which can passively agglutinate. Formalin does not allow the extrinsic platelets to secrete the vWF of their α-granules, and thus only the activity of the intrinsic vWF is tested.
Atrolysin A is an enzyme that is one of six hemorrhagic toxins found in the venom of western diamondback rattlesnake. This endopeptidase has a length of 419 amino acid residues. The metalloproteinase disintegrin-like domain and the cysteine-rich domain of the enzyme are responsible for the enzyme's hemorrhagic effects on organisms via inhibition of platelet aggregation.
Trimerelysin I is an enzyme. This enzyme catalyses the following chemical reaction
Trimerelysin II is an enzyme. This enzyme catalyses the following chemical reaction
Mucrolysin is an enzyme. This enzyme catalyses the following chemical reaction
Russellysin is an enzyme. This enzyme catalyses the following chemical reaction
